Well, my Rem 22-250 will shoot 52 gr AMAX @ 4027 fps, 55 gr FMJs at 3797 fps, RP 55 gr Factories at 3678 fps, WW 45 gr Factories at 3998 fps, 60 gr Sierras at 3460 fps - unstable/shot like crap.
I would have to guess that 26" would be the "best" for a standard 22-250. My guess would be you'd give up 50ish fps with a 24" barrel. This is of course with sloppy factory chambers. A custom, tight-neck 24" Broughton 5c will probably toast my rifle. jm2c